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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-21 11:54:28 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-21 11:54:28 +0000 |
commit | e6918187568dbd01842d8d1d2c808ce16a894239 (patch) | |
tree | 64f88b554b444a49f656b6c656111a145cbbaa28 /src/rocksdb/util/crc32c.h | |
parent | Initial commit. (diff) | |
download | ceph-e6918187568dbd01842d8d1d2c808ce16a894239.tar.xz ceph-e6918187568dbd01842d8d1d2c808ce16a894239.zip |
Adding upstream version 18.2.2.upstream/18.2.2
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/rocksdb/util/crc32c.h')
-rw-r--r-- | src/rocksdb/util/crc32c.h | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/src/rocksdb/util/crc32c.h b/src/rocksdb/util/crc32c.h new file mode 100644 index 000000000..a08ad60af --- /dev/null +++ b/src/rocksdb/util/crc32c.h @@ -0,0 +1,56 @@ +// Copyright (c) 2011-present, Facebook, Inc. All rights reserved. +// This source code is licensed under both the GPLv2 (found in the +// COPYING file in the root directory) and Apache 2.0 License +// (found in the LICENSE.Apache file in the root directory). +// +// Copyright (c) 2011 The LevelDB Authors. All rights reserved. +// Use of this source code is governed by a BSD-style license that can be +// found in the LICENSE file. See the AUTHORS file for names of contributors. + +#pragma once +#include <stddef.h> +#include <stdint.h> + +#include <string> + +#include "rocksdb/rocksdb_namespace.h" + +namespace ROCKSDB_NAMESPACE { +namespace crc32c { + +extern std::string IsFastCrc32Supported(); + +// Return the crc32c of concat(A, data[0,n-1]) where init_crc is the +// crc32c of some string A. Extend() is often used to maintain the +// crc32c of a stream of data. +extern uint32_t Extend(uint32_t init_crc, const char* data, size_t n); + +// Takes two unmasked crc32c values, and the length of the string from +// which `crc2` was computed, and computes a crc32c value for the +// concatenation of the original two input strings. Running time is +// ~ log(crc2len). +extern uint32_t Crc32cCombine(uint32_t crc1, uint32_t crc2, size_t crc2len); + +// Return the crc32c of data[0,n-1] +inline uint32_t Value(const char* data, size_t n) { return Extend(0, data, n); } + +static const uint32_t kMaskDelta = 0xa282ead8ul; + +// Return a masked representation of crc. +// +// Motivation: it is problematic to compute the CRC of a string that +// contains embedded CRCs. Therefore we recommend that CRCs stored +// somewhere (e.g., in files) should be masked before being stored. +inline uint32_t Mask(uint32_t crc) { + // Rotate right by 15 bits and add a constant. + return ((crc >> 15) | (crc << 17)) + kMaskDelta; +} + +// Return the crc whose masked representation is masked_crc. +inline uint32_t Unmask(uint32_t masked_crc) { + uint32_t rot = masked_crc - kMaskDelta; + return ((rot >> 17) | (rot << 15)); +} + +} // namespace crc32c +} // namespace ROCKSDB_NAMESPACE |